This invention relates to a disposable sanitary article such as a disposable diaper, incontinence pants or training pants and a process for attaching elastic members associated with leg-openings to such a sanitary article.
Japanese Patent Application Publication No. 1992-317650A describes a process for attaching elastic members associated with leg-openings to a sanitary article comprising steps of forming a continuous sheet along its transversely opposite side edge portions with longitudinally continuous adhesive zones, forcibly guiding a plurality of the elastic members associated with the leg-openings to extend under tension across the continuous sheet transversely thereof and bonding them to the continuous sheet in a pattern of sine curves. The elastic members associated with the leg-openings attached to the article by the process disclosed in the Publication present a stretch stress identical in front and rear waist regions except a middle zone of a crotch region.
With the sanitary article in the form of the pull-on type diaper particularly for baby, the diaper is apt to leave a space between the baby""s skin and the diaper in a front half of the crotch region due to a brisk movement of the baby. In view of this, the stretch stress of the elastic members associated with the leg-openings is preferably preadjusted to be higher in the front half than in the rear half of the crotch region. With the sanitary article in the form of the open-type diaper, in order to avoid an anxiety that the front waist region of the diaper might slip down during use of the diaper, to facilitate the diaper to be put on the baby""s body and to provide a good fit of the diaper to the baby""s body, the stretch stress of the elastic members associated with the leg-openings is preferably preadjusted to be higher on the front half of the crotch region provided with a target tape strip than on the rear half of the crotch region provided with a pair of tape fasteners. However, the elastic members associated with the leg-openings attached by the process disclosed in the Publication present a substantially identical stretch stress between the front and rear halves of the crotch region. Such feature does not make the elastic members associated with the leg-openings to have the functions required by both the pull-on type diaper and the open type diaper.
This invention aims to provide a disposable sanitary article in which a stretch stress of elastic members associated with leg-openings in a front half of a crotch region is different from that in a rear half of the crotch region and a process for attaching these elastic members associated with the leg-openings to such sanitary article.
According to one aspect of this invention, there is provided a disposable sanitary article comprising a liquid-pervious topsheet, a liquid-impervious backsheet and a liquid-absorbent panel disposed between the topsheet and the backsheet to define a front waist region, a rear waist region and a crotch region extending between the front and rear waist regions, a pair of leg-openings being defined at transversely opposite side edge portions of the article, and elastic members being secured under tension to leg-openings along the leg-openings.
The article further comprises the transversely opposite side edge portions of the sanitary article respectively which include first elastic zones extending across the crotch region in the longitudinal direction along a predetermined length, second elastic zones extending from the first elastic zones into the front waist region along a predetermined length and third elastic zones extending from the first elastic zones into the rear waist region along a predetermined length wherein the sections of the elastic members associated with the leg-openings extending along the second elastic zones and the third elastic zones has values of stretch stress represented by a relationship of the second elastic zones less than the third elastic zones or the third elastic zones less than the second elastic zones.
Another aspect of this invention relates to a process for attaching elastic members associated with leg-openings to a disposable sanitary article which comprises a liquid-pervious topsheet, a liquid-impervious backsheet and a liquid-absorbent panel disposed between the topsheet and the backsheet to define a front waist region, a rear waist region and a crotch region extending between the front and rear waist regions, and the pair of leg-openings being define at transversely opposite side edge portions of the article, comprising the steps of:
(a) feeding a continuous web having transversely opposite side edge portions forward and coating the transversely opposite side edge portions with an adhesive agent to form first adhesive zones and second adhesive zones continuously extending in a longitudinal direction of the continuous web; and
(b) feeding first and second elastic members associated with the leg-openings continuously extending in the longitudinal direction and securing sections of the elastic members placed upon the first and second adhesive zones to these zones so that the first and second elastic members extend across the first and second adhesive zones to describe a pair of continuous waveforms in a relationship of lateral symmetry, each of which is convex inward transversely beyond each of innermost side edges of the first and second adhesive zones and then convex outward transversely beyond each of outermost side edges of the first and second adhesive zones, each of the waveforms is further convex in a front or rear half of the zone in which each of the waveforms becomes convex inward transversely extending from an imaginary X-axis bisecting a longitudinal dimension of the zone than the rear or front half of the zone, the first elastic members associated with the one leg-opening lying on the first adhesive zone and the second elastic members associated with the other leg-opening are secured to the continuous web along these adhesive zones and the sections of the first and second elastic members which are convex inward and outward transversely beyond the first and second adhesive zones contract to be converged substantially into single bundles so as to move toward the first and second adhesive zones and are secured to the continuous web.
Of the disposable sanitary articles according to this invention, the article in which the elastic members associated with the leg-openings have a stretch stress preadjusted to be higher in the second elastic zone than in the third elastic zone ensures that the elastic members associated with the leg-openings present a tightening effect around the wearer""s thighs which is higher in the front half than in the rear half of the crotch region. Such feature enables the elastic members associated with the leg-openings to meet the function required by the pull-on type diaper principally used by the wearer who is brisk in movement.
Of the disposable sanitary articles according to this invention, the article in which the elastic members associated with the leg-openings have a stretch stress preadjusted to be higher in the third elastic zone than in the second elastic zone can avoid a tendency that the contractile force of the elastic members associated with the leg-openings in the second elastic zone might tend to pull the front waist region of the diaper down toward the crotch region. Such feature facilitates the diaper to be put on the wearer""s body, prevents the diaper from shifting out of its proper position during use of the diaper and provides a good fit of the diaper to the wearer""s body. In view of this, the elastic members associated with the leg-openings arranged in this manner well meets the function required by the open type diaper.
The process according to this invention for attachment of the elastic members associated with the leg-openings to the sanitary article enables the elastic members associated with the leg-openings to be continuously attached to the backsheet so that any one of the second zone and the third zones of the elastic members may have a stretch stress higher than the other.